feat: 풀스택 할일관리 앱 구현 (통합 모달 + 간트차트)

- Backend: FastAPI + MongoDB + Redis (카테고리, 할일 CRUD, 파일 첨부, 검색, 대시보드)
- Frontend: Next.js 15 + Tailwind + React Query + Zustand
- 통합 TodoModal: 생성/수정 모달 통합, 탭 구조 (기본/태그와 첨부)
- 간트차트: 카테고리별 할일 타임라인 시각화
- TodoCard: 제목/카테고리/우선순위/태그/첨부 한줄 표시
- Docker Compose 배포 (Frontend:3010, Backend:8010, MongoDB:27021, Redis:6391)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/routers/uploads.py

@@ -0,0 +1,56 @@
+from typing import List
+
+from fastapi import APIRouter, Depends, File, UploadFile, status
+from fastapi.responses import FileResponse
+
+from app.database import get_database
+from app.models.todo import Attachment
+from app.services.file_service import FileService
+
+router = APIRouter(prefix="/api/todos", tags=["attachments"])
+
+
+def _get_service(db=Depends(get_database)) -> FileService:
+    return FileService(db)
+
+
+@router.post(
+    "/{todo_id}/attachments",
+    response_model=list[Attachment],
+    status_code=status.HTTP_201_CREATED,
+)
+async def upload_attachments(
+    todo_id: str,
+    files: List[UploadFile] = File(...),
+    service: FileService = Depends(_get_service),
+):
+    """파일 업로드 (최대 5개, 파일당 10MB)"""
+    return await service.upload_files(todo_id, files)
+
+
+@router.get("/{todo_id}/attachments/{attachment_id}/download")
+async def download_attachment(
+    todo_id: str,
+    attachment_id: str,
+    service: FileService = Depends(_get_service),
+):
+    """파일 다운로드"""
+    file_path, filename = await service.get_file_info(todo_id, attachment_id)
+    return FileResponse(
+        path=str(file_path),
+        filename=filename,
+        media_type="application/octet-stream",
+    )
+
+
+@router.delete(
+    "/{todo_id}/attachments/{attachment_id}",
+    status_code=status.HTTP_204_NO_CONTENT,
+)
+async def delete_attachment(
+    todo_id: str,
+    attachment_id: str,
+    service: FileService = Depends(_get_service),
+):
+    """첨부파일 삭제"""
+    await service.delete_attachment(todo_id, attachment_id)